Closed-cycle gas laser system

ABSTRACT

A gas laser of the mixing type which separately excites an energizing gas (such as N2) and causes the mixing of a lasing gas (such as CO2) with the energizing gas in or near the optical cavity, includes a lasing gas recovery separator so as to permit closed-cycle operation. Each of the embodiments includes a primer mover such as a gas turbine or a diesel engine that operates a compressor to create the gaseous flow necessary for operating the laser. Either the prime mover, or the gaseous flow and a turbine expander, may be utilized to operate an electric generator for exciting the energizing gas. In a first embodiment, the gas effluent from the laser is first passed through a regenerative cooling heat exchanger, then through a water-cooled heat exchanger, through the compressor, and a second water-cooled heat exchanger into the carbon dioxide separator. From the separator it is passed through the coolant side of the regenerative heat exchanger, and is then warmed in a heat exchanger heated by prime mover exhaust and passed through a turbine which expands and thereby cools the flow of gas and renders it suitable for passage to the laser, the shaft of the turbine driving the electric generator. Water cooling, for the heat exchangers which use it, may be provided in an air-cooled closed-cycle water system, or by a suitable expendable source of external water. In a second embodiment, the regenerative and water-cooled heat exchangers are eliminated, a somewhat larger compressor is used, and the warmer gas is utilized as a source of heat for the stripper portion of a monoethanolamine (hereinafter &#39;&#39;&#39;&#39;MEA&#39;&#39;&#39;&#39;) absorbent, carbon dioxide separator; in other respects it is the same as the first embodiment. In a third embodiment, the electric generator and compressor are on the same shaft with the turbine, and water-cooled heat exchangers are used at the input and output of the compressor. No work is performed on or with the gas flow as it leaves the carbon dioxide separator. In other respects, this embodiment is similar to the first embodiment.

United States Patent [72] inventors Gorken Melikian Springfield, Mass.;Frank R. Biancardi, Vernon, Conn. [21] Appl. No. 858,565 [22] FiledSept. 10, 1969 [45] Patented Jan. 11,1972 [73] Assignee United AircraftCorporation East Hartford, Conn.

[54] CLOSED-CYCLE GAS LASER SYSTEM 10 Claims, 5 Drawing Figs. [52] US.Cl 331/94.5, 23/2 [51] Int. Cl Hols 3/02 [50] Field of Search 331/94.5;23/2, 3 L, 232; 55/68 [56] References Cited UNITED STATES PATENTS3,439,288 4/1969 Mangin 331/945 2,832,666 4/1958 Nertzberg et al.331/945 UX 3,391,281 7/1968 Eerkens 331/94.5 3,435,363 3/1969 Patel330/4.3 3,435,373 3/1969 Wolff 331/945 Primary Examiner Rodney D.Bennett, Jr. Assistant Exam iner N. M oskowitz Att0rney-Melvin PearsonWilliams a lasing gas (such as CO with the energizing gas in or near theoptical cavity, includes a lasing gas recovery separator so as to permitclosed-cycle operation. Each of the embodiments includes a primer moversuch as a gas turbine or a diesel engine that operates a compressor tocreate the gaseous flow necessary for operating the laser. Either theprime mover, or the gaseous flow and a turbine expander, may be utilizedto operate an electric generator for exciting the energizing gas. in afirst embodiment, the gas effluent from the laser is first passedthrough a regenerative cooling heat exchanger, then through awater-cooled heat exchanger, through the compressor, and a secondwater-cooled heat exchanger into the carbon dioxide separator. From theseparator it is passed through the coolant side of the regenerative heatexchanger, and is then warmed in a heat exchanger heated by prime moverexhaust and passed through a turbine which expands and thereby cools theflow of gas and renders it suitable for passage to the laser, the shaftof the turbine driving the electric generator. Water cooling, for theheat exchangers which use it, may be provided in an air-cooledclosed-cycle water system, or by a suitable expendable source ofexternal water.

In a second embodiment, the regenerative and water-cooled heatexchangers are eliminated, a somewhat larger compressor is used, and thewarmer gas is utilized as a source of heat for the stripper portion of amonoethanolamine (hereinafter MEA") absorbent, carbon dioxide separator;in other respects it is the same as the first embodiment.

In a third embodiment, the electric generator and compressor are on thesame shaft with the turbine, and water-cooled heat exchangers are usedat the input and output of the compressor. No work is performed on orwith the gas flow as it leaves the carbon dioxide separator. ln otherrespects, this embodiment is similar to the first embodiment.

PATENTEDJANI 1 m2 3.634.778

SHEET 1 or 3 PATENTEU JAN] 1 1972 SHEET 2 OF 3 CLOSED-CYCLE GAS LASERSYSTEM BACKGROUND OF THE INVENTION 1. Field of Invention This inventionrelates to gas lasers, and more particularly to closed-cycle systems forgas lasers of the mixing type.

2. Description of the Prior Art A recent innovation in gas lasersprovides for introducing, into the main flow through the laser, directlyat the laser cavity, a lasing gas such as C0,; the flo'w includes anenergizing gas such as nitrogen (and possibly a relaxant such as heliumor water vapor) which is energized upstream of the laser chamber.Operation of these devices in open cycle systems requires large-capacitysources of CO, and nitrogen, and result in the lasing effluent,comprising waste gas, vented to ambient.

SUMMARY OF INVENTION The object of the present invention is to provideclosedcycle operation of gas lasers of the mixing type.

According to the present invention, a closed-cycle system for a flowinggas laser of the mixing variety includes a recovery separator forseparating the lasing gas from the gas that passes through theexcitation means, together with means for providing gaseous flow throughthe system at a pressure suitable for operating the separator. Accordingfurther with the present invention, the temperature of the gas may bereduced before pressurizing. According still further with the presentinvention, the temperature of the gas before pressurizing may be reducedby a regenerative heat exchanger or by an ambient heat exchanger, orboth. According to the present invention further, the temperature of themain gas flow may be reduced after pressurization and before separation.In ac cordance further with the present invention, a temperaturereduction after separation of the gases may be effected; this may be ina regenerative heat exchanger. In further accord with the presentinvention, the main gas flow may pass through a turbine expander tobecome cooled and to assume a lower pressure; in still further accordwith the invention, the turbine may be utilized to generate electricpower for operation of the laser excitation means.

The foregoing and other objects, features and advantages of the presentinvention will become more apparent in the light of the followingdetailed description of preferred embodiments thereof, as illustrated inthe accompanying drawing.

BRIEF DESCRIPTION OF TI IE DRAWING FIGS. 1, 3, and 5 are simplifiedschematic diagrams of respective illustrative embodiments of the presentinvention; and

FIGS. 2 and 4 are schematic diagrams of separators for use in theembodiment of FIGS. 1 and 5, and of FIG. 3, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, a gaslaser 20 includes an optical cavity having mirrors 22, 24 into which isinjected a lasing gas such as carbon dioxide by means of an injectingrod or spray bar 26 which may be connected by a conduit 30 to a Cseparator 32. The gas laser 20 also receives energizing and relaxinggases (such as nitrogen and helium) from a conduit 34 which are passedthrough an excitation means such as a DC electric discharge or plasmagenerator 36. As is known in the gas laser art, the energized nitrogenassumes vibrational energy levels, and can quickly transfer energythrough resonant collisions with the molecules of CO directly within thelaser cavity, the energy level assumed by the CO being an upper laserlevel which results in spontaneous and stimulated emission of coherentlight, thus resulting in a useful laser output. The objective of thepresent invention is to provide, in a closed cycle, CO in the conduit30, and energizing and relaxant gases in the conduit 34. A furtherobjective is to do this with a minimum of expense and weight, and with amaximum of efficiency.

The outflow of the gas laser 20 is passed over a conduit 38 to aregenerative heat exchanger 40 which removes heat from the gas in theconduit 38 and adds heat to the gas applied to the heat exchanger 40 ina conduit 42. Additional aspects of the heat exchanger 40 are describedhereinafter. From the heat exchanger 40, the gas flows through a conduit44 to a second heat exchanger 46 which may be cooled by water flow ingin conduits 48, 50 which is cooled in a radiator 52 in response toambient air supplied thereto by a fan 54. From the heat exchanged 46,the cooled gas is passed by a conduit 56 into a compressor 58 which maybe driven by any prime mover, such as a gas turbine 60. The compressor58 supplies the flow energy to circulate the required gas flow in theentire system. It also results in the gas within a conduit 62 beingwarmer than within the conduit 56, so that the conduit 62 is connectedto another heat exchanger 64 which may have ambient water available atthe site, or from a cooling tower, passed therethrough from a conduit 66to a conduit 68. On the other hand, the conduits 66, 68 may be includedwithin the loop provided by the conduits 48 and 50 and thereby carrywater cooled by the radiator 52 (as is true in the heat exchanged 46).From the heat exchanger 64, the main gas flow is carried by a conduit 70into the CO separator 32 (the details of which are shown in FIG. 2 anddescribed hereinafter). With the CO separator 32, the carbon dioxide isseparated from the main gas flow so that the conduit 42 has essentiallyno carbon dioxide in it, and virtually all the carbon dioxide which issupplied to the separator by conduit 70 appears in the conduit 30. As aresult of the process within the CO separator 32 (describedhereinafter), the main gas flow (comprising substantially only theenergizing and relaxant gases) in the conduit 42 is about the sametemperature as the temperature in conduit 70. However, this gas flowpicks up additional heat in the regenerative heat exchanger 40 and in aheat exchanger 72 to which it is connected by a conduit 74. The heatexchanger 72 derives heat from the gas turbine exhaust connected theretoby a conduit 76 so that the main flow of gas in a conduit 78 is appliedto an expander (or turbine) 80 at a sufficiently high temperature sothat the expander 80 can supply the requisite power to operate anelectric generator 82. The gas turbine exhaust which flows from theconduit 76 through the heat exchanger 72 is passed by a conduit 84 tothe CO separator 32 to provide heat for the processes therein, asdescribed hereinafter. The electric generator 82 supplies electric powerto a power supply and conditioner 86 (connected thereto by wires 88)which in turn provides suitable high-voltage DC power (over wires 90) tothe electric discharge or plasma generator 36 used to excite theenergizing gas within the gas laser 20.

The CO separator 32 is illustrated in FIG. 2. Therein, the main gasstream in conduit 70 flows into an absorber tank 92, which, as is knownin the art, may comprise a plurality of trays or plates 94 having holestherein; or it can be a packed tower, as is known in the art. As themain gas flow (70) passes through the liquid within the absorber tank92, the carbon dioxide in the gas goes into solution within the liquidwithin the tank. Typically, such liquid is monoethanolamine (hereinreferred to as MEA). As the gas reaches the top of the chamber or tank92, substantially pure MEA, which may have traces of CO in it, issprayed on the gas at an inlet 96 which tends to wash out substantiallyall of the CO from the primary gas flow. The primary gas thereafterflows out the conduit 42. The MBA, with substantial CO absorbed therein,is passed over a conduit 98 by means of a suitable circulating pump I00and through a conduit 102 to a regenerative heat exchanger 104. Thepurpose of this heat exchanger 104 is to begin to add heat to the CO-rich MEA, since removal of CO from the MBA is achieved with heat. Italso cools the return flow of MBA prior to eventual reentry into theabsorber tank 92. From the heat exchanger 104, a conduit 106 carries theCO rich, warm MEA to a stripper chamber 108 wherein the CO is desorbedfrom the MEA by heat. This form of stripper is well known in the art.The prime mover exhaust gas, applied through the conduit 84 into a heatexchange element 110, provides heat to the stripper 108, that causes theoutgasing of CO from the MEA solution, the CO being passed through acold trap unit 109 (known to the art) to remove traces of possiblecontaminants (such as water and MEA) before being released from thestripper in the conduit 30 for return to the gas laser (FIG. 1). The CO,in the conduit 30 is substantially pure, depending upon properadjustment and selection of the operating parameters of the CO separator32. The high-temperature MEA, having the CO essentially all boiledtherefrom, passes out of the stripper 108 in a conduit 112, where alarge portion of its heat is given off to the CO -rich, inflowing MEA inconduit 102 via the regenerative heat exchanger 104. The somewhat cooledMEA is then passed by a conduit 114 through a heat exchanger 116 andinto the inlet 96. The heat exchanger 116 may have coolant water passedtherethrough (117), which may be ambient water, water from a water toweror water connected to the closed-loop system including the radiator 52of FIG. 1, as will suit the design expedients of any given utilizationof the present invention. As a net result of the operation of the COseparator 32, there normally is a temperature increase in the main gasflow from the conduit 70 to the conduit 42. This is due to the fact thatthe absorption of CO gas into the MEA is exothermic. There is also asmall pressure drop between the conduit 70 and the conduit 42. In orderto have the temperature of the Co -rich MEA in the conduit 98sufficiently low with respect to temperatures achievable within thestripper tank 108, it may be desirable in some instances to providecooling within the absorber tank 92, such as by the inclusion therein ofa heat exchanger 188 supplied with external coolant so as to keep thetemperature of the MEA in the absorber 92 sufficiently low. In thiscase, there can be virtually no temperature rise between the conduit 70and the conduit 42. As is known, this type of CO separator operates independence upon relative temperatures between the absorption of the COinto the MEA and the expulsion of the CO from the MEA, within certainlimits. In any event, the cooler the MEA as it enters the conduit 98,the more likely an efficient CO removal process will result. This, witha proper temperature difference and other parameters, the inlet 96 willbe supplying relatively CO -free MEA to the process, which furtherenhances the successful operation of CO separation. Also, the heatexchanger 64 (FIG. I) can bring the main gas stream in the conduit 70 tosubstantially the same temperature as the coolant in the conduit 66,thereby tending to keep the gas influx cool (such as under 100 F.). Ifthe heat exchanger 64 were not utilized, the temperature ratios withinthe CO separator 32 would have to be adjusted accordingly, possibly withsome loss of performance.

The net effect of the CO separator 32, if properly designed inaccordance with the foregoing considerations, can be accommodated by themain gas stream, other than removing CO therefrom. In other words, thereneed not be a substantial temperature change between the conduit 70 andthe conduit 42, and the pressure differential between them, althoughsignificant, is supplied by the compressor 58, in accordance with theinvention.

The operation of the system illustrated in FIG. 1 (including FIG. 2)achieves, in addition to supplying substantially pure CO, to the gaslaser 20, a removal of waste heat generated by the laser, and thesupplying of electric power to the gas laser 20. It does this inresponse to energy provided to the prime mover, such as by fuel suppliedto the gas turbine 60, and the energy sources for the fan 54 (FIG. 1)and the pump 100 (FIG. 2), which may typically be normalaltemating-current electric power, or any other suitable source. Powerrequirements of the fan 54 and the pump 100, are very small compared tothe rest of the system: therefore, essentially, the system is suppliedfuel to the gas turbine 60 and in return delivers laser energy throughone of the mirrors 22, 24.

As is known in the art, gas lasers are relatively inefficient devices.This is, the amount of energy supplied to the gas laser by the powersupply 86 far exceeds the amount of energy which may be extracted fromthe laser in the form of optical power (coherent electromagneticradiation). For instance, it has been theorized that the maximumefficiency of a gas laser is under 40 percent. Thus, if nothing elsewere done to the effluent from the gas laser 20 within the conduit 38,the waste heat appearing in the main gas flow in the conduit 38 wouldhave to be removed. Thus, the temperature of the gas in the conduit 38may be somewhere between 300 and 500 F. As it passes through the heatexchanged 40, the temperature of this gas may drop to something on theorder to l50-200 F. in the conduit 44. It is then further cooled in theheat exchanger 46 to a very near ambient air temperature, and thereforemay be at about 100 F. in the conduit 56. The compressor ratio of thecompressor 58 may vary between 4 and 16 to l; a typical ratio might bein the neighborhood of 10 or 12 to l. This depends in large part on theamount of work to be extracted from the main gas flow stream by theexpander (turbine) in generating electrical power. The heat supplied tothe gas in the compressor 58 may cause the temperature in the conduit 62to be on the order of 400 to 600 F. As described hereinbefore, afterleaving the compressor 58, the main gas stream may be further cooled inthe heat exchanger 64 to a temperature (about to F.) dependent upon theoperating conditions of the CO separator. The gas will leave theseparator in the conduit 42 at approximately the same temperature as thegas in conduit 70, so that it is capable, within the heat exchanger 40,of extracting significant amounts of heat from the main gas effluent inthe conduit 38. As the gas leaves this heat exchanger 40 within theconduit 74, it may have increased in temperature to 300 or 400 F. Theexhaust of the gas turbine in the conduit 76 may be approximately 900F., so that the heat exchanger 72 will raise the main gas streamtemperature to about 700 or 800 F. in the conduit 78. The gas turbineexhaust outflow in the conduit 84 may be roughly 300 to 500 F which issuitable for operating the stripper in the CO separator. The expander 80may have a pressure ratio on the order of8 to l, and will result inlowering the temperatures from about 700 F. to about 100 F., in atypical situation, wherein a high concentration of CO is required in thegas laser, (i.e., the main gas stream will be proportionately more COand less of other gases). In such situations a relatively small streamof gas is directed to the expander 80, which may make other embodimentsdescribed herein desirable, as is described more fully hereinafter.

As described, the embodiment of FIG. 1 achieves a primary objective inproviding for a separation of CO from other gases required by the gaslaser in order to permit operation of the mixing type of laser in aclosed-cycle configuration. Note particularly that the pressure of themain gas stream, as it enters the separator 32 can be very high, whilethe pressure of the energizing and relaxing gases in the conduit 34 asthey enter the laser can be quite low, due to the operation of theexpander 80 in converting the energizing and relaxing gases from a highpressure to a low pressure. This increases the operating efficiency andcapacity of the separator 32. Additionally, the energy resulting fromhigh pressure at the input to the separator 32 is recouped by generatingelectrical power as a result of pressure conversion in the expander 80.In addition, the inherent heat energy which is put into the main streamof gas is utilized most effectively by the regenerative heat exchanger40 converting heat at the effluent of the laser (conduit 38) intoenthalpy within the gas in conduit 74, which is recouped by the expander80 in generating electrical power (82). Additionally, a great deal ofthe enthalpy in the exhaust of the turbine, within conduit 76, is alsorecovered in the form of an increase in the enthalpy in conduit 78 foreventual recoupment as electrical energy. The remaining enthalpy in thegas turbine exhaust 84 is substantially utilized to supply the heatrequired for operation of the CO stripper within the CO separator 32, asdescribed hereinbefore.

A second embodiment of the invention is illustrated in FIG. 3. Therein,all of the elements of the system which function identically with theelements of the embodiment of FIG. 1 have like reference numerals. Themajor difference of this em bodiment is that instead of using theregenerative heat exchanger and coolant heat exchangers 46 and 64 (as inFIG. 1) the embodiment of FIG. 3 does not precool the gas prior tocompression in a compressor 130, and the main gas stream enthalpy isremoved only by use in the CO separator 132 as a source of heat(exchanger element 150) for the stripper. Assuming, as in the embodimentof FIG. 1, that the gas effluent from the laser 20 in a conduit 134 isbetween 300 and 500 F., then a larger compressor 130 is required inorder to provide a suitably high pressure in a conduit 136 for properoperation of the CO separator 132. This, to achieve the pressure ratioin the neighborhood of 12 to 14 to 1, a gas turbine 138 must be capableof supplying more power to the compressor 130 than does the turbinesupply the compressor 58 (FIG. 1). In the conduit 136, the temperatureof the main gas stream may be in the neighborhood of between 700 and 900F. As the gas leaves the CO separator in a conduit 140 it will beapproximately F, due to the cooling action of the heat exchanger 118within the absorber component of the CO separator 132. The conduit isconnected to a heat exchanger 142 to which hot exhaust gas from theturbine 138 is supplied in a conduit 144. This gas may be at about 900F. and it may result in raising the temperature of the main gas flow ina conduit 146 to approximately 700 F. The outflow of the exhaust gas ina conduit 148, which is also used as a heat source for the stripperwithin the CO separator 132, may be at a temperature of approximately450. The conduit 146 feeds the main gas stream into the expander 80which expands the gas by an amount determined by the compression ratioof the compressor 130, the pressure drop within the CO separator 132,and other pressure losses in the system. The outflow from the expander80 in the conduit 34 is somewhere between 80 and 100 F. as in the caseof the embodiment of FIG. 1.

The CP separator 132 for use in the embodiment of FIG. 3 is illustratedin FIG. 4. Therein, the primary difference between the separator 32illustrated in FIG. 2 is the provision of an additional heat exchangeelement 150, and the provision of a heat exchanger 152 which cools thegas supplied thereto over a conduit 154 from the heat exchange elementprior to passing it over a conduit 156 to the absorber 92. Thus, thetemperature of the gas is lowered markedly as it passed through thestripper.

The basis difference between the embodiment of FIGS. 3 and 4 from thatof FIGS. 1 and 2 is that a larger turbine and compressor are required,and more heat energy is rejected in the effluent from the exhaustconduit 158 (FIG. 4) as it leaves the stripper heat exchanger 110.However, less hardware is required in the embodiment of FIGS. 3 and 4.In the case where efficiency of the laser is high, or there being a highgas flow through the systemso that the effluent from the laser does notreach as high a temperature, then the embodiment of FIGS. 3 and 4 islikely to be preferable to the embodiment of FIGS. 1 and 2.

A further embodiment of the invention is illustrated in FIG. 5. Therein,a coolant system including the air heat exchanger or radiator 52 and andfan 54 includes a pair of heat exchanges 170, 172 for precompression andpostcompression cooling of the main gas stream. Specifically, a conduit174 carries the laser effluent through the heat exchanger to cool itsufficiently in a conduit 176 so that the size of a compressor 178 and,the power requirements of a gas turbine 180 which drives the compressor,can both be reduced. This, the gas in the conduit 174 may be between 400and 500 F but the gas entering the compressor 178 in the conduit 176will be at roughly 100 F. After compression, the gas in a conduit 182may be at roughly 300 F., assuming a compression ratio in theneighborhood of 4 or 6 to l. This gas then is cooled in the heatexchanger 172 so that the main stream of gas in a conduit 184 is againreturned to approximately l00 prior to entering the CO separator 32(FIG. 2, as described hereinbefore). As in the embodiment of FIG. 1, thegas leaving the CO, separator 32 in a conduit 186 may be at roughly l00F. However, the pressure, which was increased significantly by thecompressor 178 in order to facilitate operation of the CO separator 32,may be higher than desired for use in the laser 20, so that apressure-reducing valve 188 may be necessary in order to provide theenergizing and relaxing gases in a conduit 190 at a suitably lowpressure for entrance into the electric excitation portion 36 of thelaser 20. Similar to the embodiment of FIG. 1, the exhaust from the gasturbine in a conduit 192, which may be at about 900 F., may be utilizedto supply heat to the stripper portion of the CO separator 32.

This embodiment is simpler than the embodiments of either FIG. 1 or FIG.3 since it does not use an expander 80. Instead, pressure reduction atthe outflow of the CO, separator 32 prior to reentry into the laser 20is provided by a simple reducing valve 188. The embodiment of FIG. 5 mayfind its most advantageous utilization in a system in which the COconcentration in the main gas flow is relatively low, thus permitting asmaller CO separator 32; or in a system where the pressure within thelaser 20 can be somewhat higher than it may be in other embodiments.

This, the present invention provides, suitably for implementation in avariety of embodiments, a closed-cycle, flowing, mixing gas laser systemwhich compressesthe outflow of the gas laser so as to provide a suitablyhigh pressure for operation of lasing-gas-separating means, andseparately conducts the lasing gas to one input of the laser, and gasesexcluding the lasing gas, through a pressure reducer, to the other inputof the laser. A variety of heat exchange means may be used for removingwaste heat generated within the laser and maintaining minimum compressorloads.

Although the invention has been shown and described with respect topreferred embodiments thereof, it should be understood by those skilledin the art that the foregoing and various other changes and omissions inthe form and detail thereof may be made therein without departing fromthe spirit and the scope of the invention.

Having thus described typical embodiments of our invention, that whichwe claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A closed-cycle flowing gas laser system comprising:

a gas laser having a laser cavity, first inlet means for introducing atleast an energizing gas into said laser cavity, second inlet means forintroducing a lasing gas in proximity with said laser cavity, and aneffluent outlet;

a compressor;

means for separating laser gas from the remaining gases in said laseroutflow and having a first outlet means providing gas exclusive oflasing gas and a second outlet means fourth flow means for conductinggas from said compressor to said separator means.

2. The gas laser system according to claim 1 wherein said gas expandercomprises a turbine expander.

3. A gas laser system according to claim 1 wherein said gas expandercomprises an expansion valve.

4. The gas laser system according to claim 1 wherein said third flowmeans includes means connected to the effluent outlet of said laser forcooling the effluent and passing the cooled effluent to said compressor.

5. The gas laser system according to claim 4 wherein said cooling meanscomprises a regenerative heat exchanger having a heat source exchangeelement located in said third flow means and a heat sink exchangeelement located in said first flow means.

6. The gas laser system according to claim 4 wherein said cooling meanscomprises a heat exchanger with a heat sink exchange element adapted toreceive coolant from an external source.

7 The gas laser according to claim 4 additionally comprismg:

an air-cooled liquid coolant closed-cycle system; and

wherein said cooling means comprises a heat exchanger having a heat sinkexchange element connected serially within said coolant supply system.

8. The gas laser system according to claim 4 wherein said fourth flowmeans includes means connected to the outflow of said compressor forcooling said outflow and passing the cooled outflow to said separatingmeans.

9. The gas laser system according to claim I wherein said separatingmeans includes a heat-responsive stripper and wherein said fourth flowmeans includes a heat source exchange element located within saidstripper for supplying heat to said stripper prior to the passagethereby of the gases therein into said separating means for theseparation of the lasing gas therefrom.

10. The gas lasersystem according to claim 1 including aninternal-combustion-type prime mover means drivingly connected to saidcompressor for driving said compressor, and having an exhaust outflow;

and wherein said separating means includes a heat responsive stripperhaving a heat source exchange element therein, said heat source elementbeing connected to said exhaust outflow thereby to derive heattherefrom.

l I I t l

1. A closed-cycle flowing gas laser system comprising: a gas laserhaving a laser cavity, first inlet means for introducing at least anenergizing gas into said laser cavity, second inlet means forintroducing a lasing gas in proximity with said laser cavity, and aneffluent outlet; a compressor; means for separating laser gas from theremaining gases in said laser outflow and having a first outlet meansproviding gas exclusive of lasing gas and a second outlet meansproviding lasing gas; first flow means including a gas expanderconnected to said first outlet for conducting gas from said separatingmeans to said first inLet of said gas laser and for reducing thepressure in the gas therein; second flow means connected to said secondoutlet for conducting lasing gas from said separating means to saidsecond inlet of said gas laser; third flow means for conducting gas fromsaid effluent outlet to said compressor; and fourth flow means forconducting gas from said compressor to said separator means.
 2. The gaslaser system according to claim 1 wherein said gas expander comprises aturbine expander.
 3. A gas laser system according to claim 1 whereinsaid gas expander comprises an expansion valve.
 4. The gas laser systemaccording to claim 1 wherein said third flow means includes meansconnected to the effluent outlet of said laser for cooling the effluentand passing the cooled effluent to said compressor.
 5. The gas lasersystem according to claim 4 wherein said cooling means comprises aregenerative heat exchanger having a heat source exchange elementlocated in said third flow means and a heat sink exchange elementlocated in said first flow means.
 6. The gas laser system according toclaim 4 wherein said cooling means comprises a heat exchanger with aheat sink exchange element adapted to receive coolant from an externalsource. 7 The gas laser according to claim 4 additionally comprising: anair-cooled liquid coolant closed-cycle system; and wherein said coolingmeans comprises a heat exchanger having a heat sink exchange elementconnected serially within said coolant supply system.
 8. The gas lasersystem according to claim 4 wherein said fourth flow means includesmeans connected to the outflow of said compressor for cooling saidoutflow and passing the cooled outflow to said separating means.
 9. Thegas laser system according to claim 1 wherein said separating meansincludes a heat-responsive stripper and wherein said fourth flow meansincludes a heat source exchange element located within said stripper forsupplying heat to said stripper prior to the passage thereby of thegases therein into said separating means for the separation of thelasing gas therefrom.
 10. The gas laser system according to claim 1including an internal-combustion-type prime mover means drivinglyconnected to said compressor for driving said compressor, and having anexhaust outflow; and wherein said separating means includes a heatresponsive stripper having a heat source exchange element therein, saidheat source element being connected to said exhaust outflow thereby toderive heat therefrom.